Current regulating circuits are well-known in the art. Examples of such circuits are found in German Patent DE 34,05,936 A1, Austrian Patent 374,321, and European Patent 0,304,951. In addition, in "Electronics International" Vol. 55, No. 7, April 1982, pages 136 to 137, an article entitled "Parallel Power MOS FETs Increase Circuit Current Capacity" further discusses such circuits. One common application of such current-regulating circuits is in remote-control transmitters with an infrared diode as the emitting device used, for example, to control televisions and other consumer electronic products. Since such remote-control transmitters are generally battery operated, the transmitting power of the infrared output stage is heavily dependant upon the respective battery condition. A current regulating circuit is necessary to conserve the battery power and to maintain relatively constant transmitting power. However, most conventional current-regulating circuits suffer from the drawback that a considerable part of the supply voltage across the control path is lost in devices for sensing the respective current. This reduces the extent of utilization of the battery's capacity and diminishes the transmitting power at an early time as the battery voltage decreases.
It is, therefore, an object of the present invention as claimed to provide a current-regulating circuit for a resistive load whose current-sensing device and regulating circuit are designed so that the voltage drop across the control path is minimized. The voltage requirement of the controller of the control path must, accordingly, not be greater than the voltage drop across the series combination of the resistive load and control path.
It is a further object of the present invention to improve the operation of the current-regulating circuit so that pulsed operation with regulated current amplitude is possible, with the turn-on and turn off edges of the current pulses being as steep as possible so that the individual pulses can be kept as narrow as possible in order to save current and minimize power dissipation, and in addition, to achieve high transmission frequency.